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8930 zfs_zinactive: do not remove the node if the filesystem is readonly

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illumos/illumos-gate@93c618e0f4

https://www.illumos.org/issues/8930:
We normally remove an unlinked node when its last user goes away and the
node becomes inactive. However, we should not do that if the filesystem
is mounted read-only including the case where it has its readonly
property set. The node will remain on the unlinked queue, so it will
not be leaked.

One particular scenario is when we receive an incremental stream into a
mounted read-only filesystem and that stream contains an unlinked file
(still on the unlinked queue). If that file is opened before the
receive and some time later after the receive it becomes inactive we
would remove it and, thus, modify the read-only filesystem. As a
result, the filesystem would diverge from its source and further
incremental receives would not be possible (without forcing a rollback).

Another related scenario, that may or may not be possible depending on an
OS / VFS policy, is when an open file is unlinked, then the filesystem is
remounted read-only, and then the file is closed.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Gordon Ross <gwr@nexenta.com>
Author: Andriy Gapon <avg@FreeBSD.org>
This commit is contained in:
Alexander Motin 2018-01-21 23:42:45 +00:00
parent ebd7699264
commit dbee84cc27
1 changed files with 26 additions and 7 deletions
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33
uts/common/fs/zfs/zfs_znode.c
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@ -1250,9 +1250,21 @@ zfs_rezget(znode_t *zp)
return (SET_ERROR(EIO));
}
zp->z_unlinked = (zp->z_links == 0);
zp->z_blksz = doi.doi_data_block_size;
/*
* If the file has zero links, then it has been unlinked on the send
* side and it must be in the received unlinked set.
* We call zfs_znode_dmu_fini() now to prevent any accesses to the
* stale data and to prevent automatical removal of the file in
* zfs_zinactive(). The file will be removed either when it is removed
* on the send side and the next incremental stream is received or
* when the unlinked set gets processed.
*/
zp->z_unlinked = (zp->z_links == 0);
if (zp->z_unlinked)
zfs_znode_dmu_fini(zp);
ZFS_OBJ_HOLD_EXIT(zfsvfs, obj_num);
return (0);
@ -1314,14 +1326,21 @@ zfs_zinactive(znode_t *zp)
mutex_exit(&vp->v_lock);
/*
* If this was the last reference to a file with no links,
* remove the file from the file system.
* If this was the last reference to a file with no links, remove
* the file from the file system unless the file system is mounted
* read-only. That can happen, for example, if the file system was
* originally read-write, the file was opened, then unlinked and
* the file system was made read-only before the file was finally
* closed. The file will remain in the unlinked set.
*/
if (zp->z_unlinked) {
mutex_exit(&zp->z_lock);
ZFS_OBJ_HOLD_EXIT(zfsvfs, z_id);
zfs_rmnode(zp);
return;
ASSERT(!zfsvfs->z_issnap);
if ((zfsvfs->z_vfs->vfs_flag & VFS_RDONLY) == 0) {
mutex_exit(&zp->z_lock);
ZFS_OBJ_HOLD_EXIT(zfsvfs, z_id);
zfs_rmnode(zp);
return;
}
}
mutex_exit(&zp->z_lock);